A natural anti-corrosion agent from seaweed

[India] Seaweed can now help protect the steel body of ships from corrosive bacteria. Researchers from Bharathidasan University, Tiruchirapalli, have reported that seaweed extracts can kill fouling agents like barnacles and biofilm-forming bacteria.

With the International Maritime Organization (IMO), London, completely banning the use of chemicals as anti-fouling agents, there is an urgent need to develop environment-friendly paints that serve the purpose. As seaweed is known to be rich in compounds such as lipopeptides and amides, the researchers examined their potential as anti-corrosion agents.

Ten different varieties of seaweed were collected from different locations in the southeast coast of India. Their bioactive compounds were extracted using different solvents and tested against barnacles and biofilm-forming bacteria. The extract from the seaweed Turbinaria ornata proved to be an effective anti-corrosion agent on mild steel — the metal used for building ships and other marine structures.

The extract showed high anti-microbial activity against eight different biofilm-forming bacteria collected from the base of ships. At a concentration of just 25 g/l, the extract showed nearly 100% inhibition of bacterial growth on mild steel. The 10-Octadecaonic acid present in the seaweed was found to inhibit corrosion. The results were recently published in Scientific Reports.

When tested against barnacle larva, 400 microgram/mL of the extract caused about 100% mortality in 12 hours. “After a biofilm is formed on the hull of the ship, a solution known as pickling solution is now being used to remove it. But this solution leaches out some of the metal as well. Our new extract was able to remove the biofilm alone without harming the metal,” explains Muthukumar Krishnan, post-doctoral fellow at NIT Tiruchirapalli and first author of the paper.

“There is a huge economic loss due to biofouling. It adds to the drag force of the ship, thus increasing fuel consumption. The current anti-fouling agents are rich in chemicals and highly toxic to the environment. Our new extract is completely natural and thus eco-friendly,” explains Dr Arthur James from the Department of Marine Science at the University and corresponding author of the paper.

“Further tests need to be carried out to optimise the formulation so that it can be mixed with paints and used on ships and other marine structures.”

Photo: “Our new extract is completely natural and thus eco-friendly,” explains Arthur James